Communication systems are known to comprise a plurality of communication units arranged into communication groups, a limited number of communication resources, and a communication resource allocator. The communication resource allocator allocates the communication resources, as voice channels, to particular communication groups upon a request from one of the communication units in the group. The communication unit makes the group call request by transmitting a group call request to the communication resource allocator via a control channel, wherein the control channel is one of the limited number of communication resources which transceives communication system information between the plurality of communication units and the communication resource allocator. (Note that a communication resource may be a carrier frequency, a pair of carrier frequencies, a time division multiplex (TDM) slot, or any other RF medium.) When a voice channel is allocated to the particular communication group, every member of the group may participate in the communication via the allocated voice channel. When the group call ends for the particular group, the voice channel is de-allocated such that it may be allocated to another communication group.
In recent years, technological advances have allowed several communication systems to be linked together via a central controller to form a communication system network. In the communication system network, the central controller allocates the communication resources in each communication system (or communication site) to the communication groups. Thus, a communication group call may be established in several communication systems such that the members of the communication group may be located in any one of the communication systems and still participate in the group call. For example, if the communication system network comprises four communication systems, wherein a member of a particular talk group is located in each communication system, a communication resource will be allocated in each system to the group. The central controller will then link the allocated communication resources together such that the group call may occur throughout the communication system network.
Even more recently, technological advances now allow, during a communication group call, multiple communication units to talk at one time and have their audio summed together by a processing multiplexer switch. The processing multiplexer switch is fully described in U.S. Pat. No. 5,175,727, assigned to Motorola. However, the use of the processing multiplexer switch with the communication system network is presently being designed and requires establishment of communication processing information by the central controller of the communication system network; wherein the communication processing information includes information of the sourcing (transmitting) communication unit, or units, and information of the destination (receiving) communication unit, or units. This information needs to be transferred to the processing multiplexer switch and must take place in a relatively short period of time such that no noticeable delay is detected by the operators of the communication units. Therefore, a need exists for a method that allows communication processing information to be transferred between the central controller of the communication system network and the processing multiplexer switch.